This invention relates to a process for the control of the withdrawal of a casting from a cooled, horizontal, continuous casting mold made from a material of elevated heat conductivity, wherein (a) the casting is withdrawn in steps from the mold, (b) the metallic melt, e.g. steel melt, arrives discontinuously in the mold and, (c) following the formation of the casting skin and each withdrawal step, the casting is pushed back by a partial step.
In the case of horizontal, continuous casting, the casting that is formed with metals having an elevated melting point is withdrawn in steps from a stationary or movable horizontal mold. Between the individual steps there is a stoppage or idling period, or the casting is pushed back by a partial step. This mode of operation is followed in order to bring about a welding of the casting skin that is formed directly from the melt with the casting skin that has already been formed and that has already been withdrawn by one step. If a complete welding does not occur, there exists the danger that the newly formed casting skin will remain at the beginning of the mold and that between it and the casting skin that has already partially solidified, there will exist some liquid melt which, upon a subsequent withdrawal of the casting, might emerge from the mold. If such a so-called "breakthrough" of the casting does occur, the continuous casting process must be interrupted. Apart from the great hazard to operating personnel and equipment such a breakthrough produces, there is also a substantial interruption of production.
To prevent a casting breakthrough there is already known a process for continuous casting in which the temperature is measured at the mold wall directly at the point of entry of the melt into the mold. If the temperature drops by 8.degree.-25.degree. C. below a predetermined temperature, the casting is held stationary until a rise in temperature can again be recorded. While it is true that it is possible with this process to perform a controlled withdrawal of the casting as a function of the formation of the casting skin, the delays between the failure of the casting skin sections to weld and the measurement of the consequent temperature drop are so great that a breakthrough of the melt out of the mold cannot be reliably prevented. The drawback with this process is that the temperature is measured at the wall of the mold, but this temperature is a function of the quantity of heat reaching the measuring point. The quantity of heat that reaches the measuring point, however, is not a result of thermal radiation, but of heat conduction, which requires a substantial amount of time.
Another process for the stepwise withdrawal of the casting from a horizontal continuous casting mold is known from German Patent No. 2,340,636. In that process the withdrawal and the casting stoppage or idling periods are controlled by the torque of a motor. With this control the basic assumption is that an inadequate cooling of the casting skin will cause it to adhere to the wall of the mold, thereby causing a greater resistance to withdrawal. The drawback with this process is that, in the event of an absence of welding of the freshly formed casting skin with the casting skin previously withdrawn, there is not a greater resistance to withdrawal, only a significantly smaller resistance, so that in this case the hazard also exists that the melt may emerge through casting skin.